SPEC SHEET TERMS
Understanding the lingo of a particular welding machine’s literature brochure or specification sheet can be a bit confusing if the hobbyist is also new to welding. To that end, I’ll bring some clarity to the jargon you are likely to come across, regardless of the manufacturer, when reading a machines capabilities and electrical requirements.
CONSTANT VOLTAGE vs CONSTANT CURRENT
A constant voltage (CV) machine is capable of only two wire processes; GMAW (Gas Metal Arc Welding aka MIG; Metal Inert Gas) and FCAW (Flux-Cored Arc Welding, the two types being self-shielded and gas-shielded). While GMAW and FCAW have similarities, their required CV power source will not work for any other processes (eg. stick, TIG) and are therefore not referred to as “multi process” power sources.
A constant current (CC) power source is capable of both the GTAW (Gas Tungsten Arc Welding aka TIG; Tungsten Inert Gas) and SMAW (Shielded Metal Arc Welding aka stick) processes. While the stick and TIG process are vastly different, the constant current power source is still not considered a multi process power source because it is not capable of any running wire processes.
A multi process power source, therefore, would be one that provides both constant voltage and constant current output for all the processes discussed above.
POLARITY
Polarity describes the required “charge” of the electrode for a particular welding process and often in conjunction the alloy that process is being used on. While there are rare exceptions to the rules below, here is the polarity guideline for CV & CC processes:
CV: GMAW & FCAW (gas-shielded) > DC+, FCAW (self-shielded) > DC-
CC: SMAW > DC+ or AC depending on electrode type
CC: GTAW (aluminum, magnesium) > AC, GTAW (all alloys other than Al &Mg) > DC-
INPUT VOLTAGE & PHASE
With a few exceptions, the majority of low output hobbyist machines will run on very common 120V which is almost everywhere and is always single phase only. The “exception” machines may run on 208 or 230V which may accept single phase, 3 phase or both depending on its design. A machines spec sheet will tell you the input requirements/options. One important takeaway here is that any single phase power source can run on a 3 phase outlet with a correctly configured plug. The opposite, however, is not true.
RATED OUTPUT & DUTY CYCLE
Duty cycle measures the “robustness” of a machine at some amperage; that is, the number of minutes you can weld continuously (duty cycle %) at a given amperage before it’s designed to shut down to avoid overload damage. While a machine, for example, may have an amperage output range of 40 – 150 A, it may have a duty cycle of 60% at 100A. We can surmise that the duty cycle at 150A will be lower, but we don’t know how much lower. The output/duty cycle relationship is meant to give the operator a relative idea of the capacity (think “wall thickness”) of the machine. This relationship will also determine if a machine is hobbyist, light industrial or heavy industrial.
CONCLUSION
There is, indeed, a lot to digest here… and it’s impossible to come to a conclusion of “what’s right for you” without some context of your welding application(s) and expectations. If this is the case, I suggest that you speak to one of our well trained store professionals in person.
Next Read: Hobbyist MIG Welder Buying Guidelines: Input Voltage, Amperage Output & Weight
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